JPH0445071A - Duplex printer - Google Patents

Abstract

PURPOSE:To promote space-saving as well as to improve the registration in each printing part of both sides by detecting a sheet end in parallel with the conveying direction at the vicinity of a reversible roller during sheet turnover operation, and making this reversible roller so as to reciprocate in the axial direction so as to make the sheet end accord with this sensor position. CONSTITUTION:A sheet 21 is fed to a contact part of a turnover roller 2 in a stopped state, and a tip of the sheet 21 is parallelly set to a roller shaft. Next, this turnover roller 2 is driven. When a sheet travel sensor 3 detects a sheet terminal, the turnover roller 2 comes to a stop. When a sheet end detecting sensor 4 is turned on at this point of time, the sheet 21 is situated in a more upper position than this sheet end detecting sensor 4, so that the turnover roller 2 is shifted in the opposite direction to the sensor 4 in a state of holding the sheet in between. In contrast with this, at time of being off, it is moved in direction to the sensor 4 till it is turned on. Thus, a sheet end is accurately positioned, and a correction of each printing position of both sides can be done in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a double-sided printing device, and more particularly to a paper positioning mechanism for backside printing in this type of printing device.

[Conventional technology]

Before explaining the present invention, an example of a laser beam printer capable of one-sided printing is shown in FIG.

In FIG. 4, sheets 21 loaded in a hopper 20 are separated and conveyed sheet by sheet by a pickup roller 22, then sent to a transfer section 24 by a foot row 2; 3, and transferred to a photosensitive drum 25. , I-'s 1-car is paper 2
．． No. 1J is transcribed.

Next, the paper 2] passes through the fixing roller 26, so that the toner is fused to the paper 21, and the printing on the surface is completed.

The paper 21- that has passed through the fixing roll 26 passes through the bus gate 2.
7, the paper is guided to the to side passage of the bus gate 27 and is once bit into the paper reversal row 2 (forward/reverse rotation row 2).

When the last end of the paper 21 passes over the paper feed sensor 3 provided at the front stage of the reversing roller 2, the reversing row 2 immediately starts reversing, and the paper 2 is fed into the paper return 2 path 28. .

The next [-1 sheet 2] is transferred to the transfer section 24 again. &: sent, 1
Printing is performed on the front side.

After that, the paper 21 passes through the fixing roller 2.6 again, and is guided to the pass gate 2.7c, this time through the pass gate 2.7c. , to the stacker 29], printing on the front and back oil surfaces is completed.

By the way, printing is possible using the process described above.

In a double-sided printing device that is used for double-sided printing, ideally all two paper feed rolls such as the pickup roller 22 and feed roller 23 for feeding the paper 21 should be arranged in parallel, but in reality, In this case, minute mechanical errors due to parts precision etc. accumulate, resulting in deviation in parallelism between the respective rollers.

This misalignment is caused by the inclined feeding of paper 2.
Further, since the paper 2.1 is fed diagonally, the feeding position of the paper 21 gradually moves to 2. It should be noted that the further the paper passes in the f direction, the more rollers it passes, and the more the mechanical error accumulates. .

Therefore, the most paper path is 1st stream I, position 19. In the paper return path 28 where the paper 21 is tilted j9 and the feeding position zuo, the maximum h rate is high, and the print position on the front surface is 1.11 sentences + i' 1. ,,I noticed that the printing position on the back side was distorted, so I came here to correct this defect, and here we go! ') As shown in the figure 1. knee, the paper return (7 passage 28
An inclined roller 40 and a guide plate 41 for guiding the edge of the paper are installed inside, and while feeding the paper 21, the paper 21 always returns so that the edge of the paper 2]- is along the guide plate 4]. The feeding position of the paper was corrected, and the printing positions were aligned on the front and back sides of the paper 2].

[Problem to be solved by the invention]

However, according to this method, when attempting to effectively correct the position of large-sized paper (for example, A3 size) or thick paper, a relatively horizontal paper path of less than the maximum length of the paper is required. 4, the length of the paper return path becomes long, and the overall size of the machine increases accordingly.

In addition to this, if the deviation of the paper running position becomes too large, the correction may not be completed. In addition, if an attempt is made to correct a large deviation in the paper traveling position, the paper path length must be further lengthened [2], and further enlargement of the machine is unavoidable.

[1] The object of the present invention is to eliminate the drawbacks of the prior art described above and to
The purpose of the present invention is to provide a double-sided printing device that is space-saving and that can reliably align the printing positions on the front and back sides of a sheet.

[Means to solve the problem]

The purpose is to have a paper return path for returning the paper to the printing mechanism section again after printing on the front side and printing on the back side, and to have a forward/reversible mechanism in which the front and back sides of the paper are reversed. In a duplex printing device having a paper reversing unit consisting of a pair of rollers, the paper edge is detected near the forward and reverse rollers of the paper reversing unit and at a position parallel to the paper feeding direction where the paper edge should pass. In addition to providing a detection sensor, a drive unit that moves the forward and reverse rollers back and forth in a direction perpendicular to the paper feeding direction is also installed. This is achieved by providing a forward/reverse roller position movement control means to match the position of the forward/reverse rollers. Focusing on the fact that it is held between forward and reverse rollers, by moving this roller in the axial direction,
This allows the sheet to be moved in the feeding direction 7j.

[Example] Hereinafter, the present invention will be explained based on the embodiments shown in FIGS. 1 to 3. FIG. The perspective view, FIG. 2, and FIG. 3 are diagrams for explaining correction of the paper feeding position.

In FIG.
For example, a reflective optical sensor is used for the paper feed sensor 3, and a paper edge detection sensor 4 is used for the paper feed sensor 3.
For example, a transmission type optical sensor is used.

Further, the reversing roller 2 is configured so that it can be reciprocated in the roller axial direction (in the direction of the arrow in the figure) by a motor 5 capable of forward and reverse rotation.

In the figure, 6 is a pinion gear attached to the motor 5,
7 is a belt that inverts the rotational force of a pinion gear [; 8 is a loom, and 9 is a motor] and transmits it to the gear 2; 10 is a 2-turn reversing roller via a frame 8, which reciprocates in the direction of the arrow shown in the figure; 1 is the vapor guide and 21 is the paper.

Here, the paper feeding position correction operation in this configuration will be described above.

In order to align the printing position on the back side of the paper with the front side of the paper, there are two steps: a tilt correction to correct the paper 2 which was fed at an angle so that it is parallel to the feeding direction, and a correction to compensate for the shift in the paper feed position due to the inclined feed. Correction is required.

In the second embodiment, a conventionally known roller abutment correction force method is used to correct the parallelism of the sheet 2.

That is, the reversing roller 2 is stopped 1: when the liquid comes into contact with the liquid 1. Guide the leading edge of the paper 21.

By feeding the paper 21 into the paper 21, the leading edge of the paper follows the roller contact area, and the leading edge of the paper 21 follows the roller contact area.
U-axis do NJ', edit one line. Next, the reversing roller 2 is rotated from this state, and the paper 21 is fed until the paper travel sensor 3 detects the end of the paper.

However, the end of paper 2 was detected at -), and the reversing roller 2
When the paper 2 stops, the paper 2] is reversed [ ]-ra 2,mu," and stops in a pinched state, and at this point the paper edge detection sensor 4
is in the ON state, the second figure 5. As shown, the paper 2] is at the predetermined feeding position (the detection position W of the paper edge detection sensor 4).
), the motor 5 shown in FIG. Move it in the direction of the arrow in the figure. On the other hand, as shown in FIG. 3, when the paper edge detection sensor 4 is in the OFF state, the paper edge detection sensor 4 is
The reversing roller 2 moves from FF to ON position.
is moved in the direction of the arrow in FIG. (Refer to 8), and the correction operation of the printing position on the back side of the paper is completed! do.

In addition, in the above embodiment, the case where a transmission type optical sensor is used as the paper edge detection sensor 4 is illustrated, but
The paper edge detection sensor 4 (CCI) sensor is used to directly detect the amount of deviation of the paper edge, calculate the operating amount of the motor 5 that reciprocates the reversing roller 2, and calculate the result of this calculation.1. 7 may also be used to control the motor 5 to operate more.

Further, in the above embodiment, the feeding position correction operation of the paper 21 is performed when the reversing roller 2 once stops. However, if the paper 21 is held between the reversing rollers 2, Even if paper 21 is being sent,
The feeding correction operation can be performed.

〔Effect of the invention〕

The present invention is as follows 1-, and as is clear from the description of the illustrated embodiments, according to the present invention, the paper reversing mechanism section can be provided with a paper feed positioning function, so that the paper size It is possible to obtain a double-sided printing device that saves space and is capable of reliably aligning the print position on the front and back sides of a sheet without being limited to types such as thickness or the like.

[Brief explanation of the drawing]

Figures 1 to 3 show an embodiment of the duplex printing apparatus according to the present invention, Figure 1 is a perspective view of the paper reversing mechanism, and Figures 2 and 3 explain how to adjust the paper feeding position. FIG. 4 is an explanatory diagram of the internal structure of a laser beam printer, which is an example of a double-sided printing device, and FIG. 5 is a perspective view showing an example of a paper alignment mechanism in a conventional double-sided printing device. 1 is a motor, 2 is a reversing roller, 3 is a paper feed sensor, 4
is a paper edge detection sensor, 5 is a motor, 6 is a pinion gear,
7 is a rack gear, 8 is a frame, ]-〇 is a slide rail, and 21 is paper. ) 2 figures rice 3 figures) 4 figures 5 figures se

Claims (1)

[Claims] 1. After printing the front side, return the paper to the printing mechanism section,
In a duplex printing apparatus, the duplex printing apparatus has a paper return path for performing reverse side printing, and a paper reversal section in the paper return path, which is composed of a pair of rollers capable of forward and reverse rotation, and which reverses the front and back sides of the paper. A paper edge detection sensor for detecting the edge of the paper is provided near the forward/reverse roller and at a position parallel to the paper feeding direction where the edge of the paper should pass, and the forward/reverse roller is moved back and forth in a direction perpendicular to the paper feeding direction. What is claimed is: 1. A double-sided printing device comprising: a driving section; and a forward/reverse roller position movement control means for aligning the edge of the paper held by the forward/reverse rollers with the position of a paper edge detection sensor during paper reversal operation.